An inlet check valve for use with high pressure cylinders, for example, up to 40,000 psi or greater, must be capable of operating reliably at such high pressures. One example of an inlet check valve assembly is described in U.S. Pat. No. 4,371,001 which discloses an inlet valve mounted on the end of a projecting portion of a generally cylindrical check valve body. The inlet check valve has a valve element that is mounted over an inlet passage. The inlet valve element tapers from a lower larger diameter to a thin shaft that is pressed into an opening on one end of a leaf spring. The opposite end of the leaf spring is secured to the projection of the valve body by a mounting screw extending through a spacer into a threaded hole in the valve body. The spacer has a height equal to the height of the valve element such that the leaf spring is approximately perpendicular to the center lines of the mounting screw and the valve element. Such a check valve normally functions well in service, however, the design does have several disadvantages. First, the leaf spring is capable of rotation with respect to its mounting screw. Therefore, the valve element may be installed off-center with respect to the inlet passage, or the valve element may be moved off-center during operation of the cylinder pump. When the valve is off-center and misaligned with the inlet passage, the valve element is subjected to uneven wear and overheating. In addition, the leaf spring can bend or otherwise inhibit the valve from having the proper lift, thereby potentially causing overheating and reducing pump efficiency. Further, the assembly of the valve element and leaf spring must be replaced whenever the valve element itself must be replaced, thereby increasing the cost of valve replacement. Consequently, there is the need for an improved inlet check valve.